Chromatics - Chilled out electronic music that sounds like everything has a purpose, not just mindless loops designed to get radio plays. Spotify link

Marika Hackman - Folk music with hints of mediaeval styles and scales. Well sung and manages to stay interesting after multiple listens instead of being two-dimensional like some folk can be. Free album stream here

Also, another vote for AlunaGeorge, for managing to mix pop and R&B and still sound fresh.

EDIT: OH, and The Weeknd! Makes hip-hop but is actually a skilled vocalist that hits some brilliant notes. Maybe not to everyone's taste, but give him a try. www.youtube.com/watch?v=o9PuAm7d0PA